Perceptual adaptation to prism displacement has been assessed by several different means according to the type of coordination being considered. These include a measure of eye-hand coordination (termed the negative aftereffect - NA), a measure of head-hand coordination (termed the proprioceptive shift - PS), and a measure of eye-head coordination (termed the visual shift - VS). When proprioceptive feedback is reduced or eliminated, PS magnitude is reduced and is replaced by an enhanced amount of VS. In Experiment 1 subjects will point (in a slow or a fast manner) to a target location either laterally or ballistically and will be given error-corrective feedback only at the terminus of a response during prism exposure. In addition, arm movement will either by actively or passively controlled. It is predicted that PS will be optimal with active, lateral, and slow arm movement toward a target location. Experiment 2 introduces hypnotic anesthesia in the subject's adapting arm during prism exposure to determine if, as in previous research, this manipulation reduces the magnitude of PS and if this is the case, whether VS is enhanced in magnitude. Experiment 3 will also use hypnotic anesthesia either during the entire adaptation period (preexposure, exposure, and postexposure) or only during the exposure period. In addition, either slow or fast ballistic and lateral arm movement will be observed during prism viewing. Enhanced PS is predicted to occur if a subject localizes a target position in a slow ballistic manner during prism viewing with or without hypnotic anesthesia in the adapting arm. However, if lateral, nonlocalizing arm movement is observed during prism viewing with the arm anesthetized, a considerable decrease in PS is expected. Experiment 4 will be concerned with investigating the nature of the VS. This will be assessed as a function of eye position during prism viewing, either a maintained straight ahead gaze or active visual tracking of a moving target to the straight ahead position. It is predicted that the latter will produce the greatest magnitude of VS. If this is the case a theoretical reinterpretation of this component of adaptation will be made.